Rubber cement



Patented Oct. 6, 1942 U NI T E D- STATES PAT E OFF [C E uss an CEMENT No Drawing.

Application October 17, 1938,

Serial No. 235 1 59 59-259 9 Claims.

My invention relates to improvements in adhesive cements, and more particularly, to heat vulcanizing rubber cements containing rubber in an organic solvent.

Rubber cements are largely used in industry as adhesives, for coating fabrics followed by drying and vulcanizing, and also for the manufacture of rubber articles by single or multiple dipping of molds or'forms in the cement followed by the drying of each mold separately and vulcanizing the Whole.

The simplest type of rubber cement consists of rubber dissolved in an organic solvent such as naphtha, gasoline, benzol or carbon tetrachloride. Many other substances may be added to such cements, however, in order that desirable properties may be imparted to the cement. Certain rubber non-solvents such as alcohols, esters, ketones, sulfonated hydrocarbons, and the like, are often incorporated into rubber cements in order to reduce their viscosity and thereby permit, if desired, the incorporation therein of additional rubber. Fillers and softeners may also be added such as mineral oil, carbon black, clay and pigments, The heat vulcanizing cements also contain culvanizing agents such as sulfur, selenium or tellurium, and accelerators such as diphenyl guanidine, polybutyraldehyde-aniline or zinc dibutyl dithiocarbamate and an activator such as zinc oxide or stearic acid.

It has been necessary in the past with the heat vulcanizing rubber cements to make them up in two different portions, one solution generally comprising rubber, solvent, zinc oxide,and the vulcanizing agent and the other comprising rubber, solvent, zinc oxide, and the accelerator. The two solutions are then mixed just before use. This is necessary since the complete rubber cement containing the vulcanizing agents and the accelerator spontaneously tends to form irreversible gels, or vulcanize, after standing for a short time. Since the cement in this vulcanized gel form is not afiected by the ordinary rubber solvents it is no longer utilizable as a cement and hence it has formerly been necessary either to make up only the amount of cement required for a particular job, or else discard the unused portion. This spontaneous vulcanization of the rubber cement at ordinary temperatures is entirely different from the gelling of non-vulcanizing cements. Cements of the latter type form reversible gells which may be dissolved by additional solvent or which may be inhibited by viscosity reducing agents such materials as acetone, ethyl alcohol, nitrobenzol, etc. These viscosity reducing agents have no beneficial effect with respect to inhibiting the irreversible gelling, or vulcanizing, of heat vuloanizing cements on storage at ordinary temperatures.

In my copending application U. S. Serial No. 145,786, filed June 1, 1987, I have disclosed the use ofnitroparaflins as inhibitors for the irreversible gelling or vulcanization ofheat vulcani'zingrubber cements. "I have now discovered that the addition of halogenated nitroparafiins to rubber cements of the heat vulcanizing types will likewise permit the mixing or 'thetwo components and give stable solutions which will not form irreversible gels'or'vul'canize, on long periods of standing at atmospheric temperature. I have further discovered that the addition of these halogenated nitroparaflins does not deleteriously affect the vulcanizing properties of the cements, and gives solutions stable over longer periods of time than are obtainable with the nitroparaflins. While I have found that the halogenated nitroparaffins in general are effective as *inhibitors for tneirreversjib e s ll or vul ization of heat-vulcanizing rubber cement, I prefer to utilize the chloroand bromonitroparaffins, containing'not more than eight carbon atoms, and particularly- I-chlQro-I-nitroethane, l-chloro l-nitropropane, and 1-bromo-1-nitropropane.

According to the present invention the complete rubber cement. may be prepared in one solu tion" and the. halogenated nitroparaffin incorporated in any desired'manner'therein. The rubber stock may be prepared by incorporating the vulcanizing agent, the acceleraton'the softener, and theYfilling material with the rubber, and the whole dissolved in some suitable solvent such as benzol, varnish and paint makers naphtha, carbon tetrachloride or ethylene dichloride. To this solution a suitable amount of the halogenated nitroparaffin may be added which is suflicient to prevent the cement from spontaneously forming vulcanized gels' on standing at {atmospheric temperature. It may be'desirable in certain instances to. add the halogenated'nitroparafiln directly to the rubber solvent before dissolving the rubber therein.

My invention may be illustrated by the following specific examples: 1

Example I The following rubberstock was prepared by mill mixingz' Parts by .Ingedlent weight Raw rubber Sulfur Zinc oxide Zinc dibutyl dithiocarbamate Polybutyraldehyde-aniline accelerator.

tained at a temperature of 82 F. for a period of 90 days, and the time of formation of a vulcanized gel was noted. The following results were trations equivalent to by weight of rubber; Various concentrations of l-chloro-l-nitropropane were incorporated in separate portions of secured: these solutions, and the resulting solutions were 5 observed for a period of 12 days at 122 F. The Ghloronitro 'oompoima Gelling tim'e following results were secured:

Blank -.i 95ll0lllS. Ooncen- -clgloro-l-nitropropane. N o iggl in 90 days. tralsion of -c oro- -ni ropropane.. '0. c loro- 3-chloro-l-nitropropane D0. nitrocomi Ohloronitro compound poundi 1 Parent sofiititn Stilts? The above example is representative of the y a results obtained at atmospheric temperature. 5013mm The vulcanized gelling, however, is accelerated r at elevated temperatures, and for test n pur- Blank 0 33. 13s. poses such elevated temperatures may be eml g filgigiglgg ig gg lg ployed with considerable saving in time. In the p p 7 12 Es s. following examples the tests were made at a teml'chloro-l'mtmpmpane 10 g perature of 122 F. days.

Example II The following rubber stock was prepared by Example V n mixing; The rubber stock employed in Example II was dissolved in ethylene dichloride in a concen- Parts tration equivalent to 5% by weight of rubber. Ingredient by One portion of the solution was employed as a We1g blank, and l-chloro-l-nitropropane was added R bb 100 to another portion of the solution in a concen- Q er Z5 tration of 5 per cent by weight. The resulting 5 solutions were observed over a period of 12 days ld'h b t 0.5 3$g i ggiggfi g M at 122 F., and the followlng results were secured:

The above stock was dissolved in benzol in a concentration equivalent to 5% by weight of rub- 0111mm") compound Gelling time ber. One portion of the solution was utilized u :1 Blank 87 hours. as a blank and v r s hl r mtr compounds l ehloro l mtmpmpane No gem 12 days. were incorporated in separate portions of the solution, in a concentration of 5%, based on the Exam Z VI Weight of the solution. The various resulting 6 solutions were maintained at a temperature of 40 e rubber Stock employed in p e II was 122 F. for 12 days and the time of formation dissolved in benzol and in naphtha in concenof a vulcanized gel was noted. The following trations equivalent to 5% by wei t Of rubber. lt were d; Approxlmately 5% of l-chloro-2-methyl-2-nitrobutane, based on the weight of the solution, Chloronitm compound Genmg time was incorporated in portions of each of the solutlons, and the solut1ons were observed over a Blank 38 11mm period of 12 days at 122 F. The following rel-chloro-l-nitroetha No gel in 12 days. sults l-l-dichloro-l-nitroeth Do. were secured l-cgloro-gniiropropana 80 11Do. 5 0 2-0 oroni ropropane Ours; G Inn 1; G11 t l-l-dichloro-l-nitropropane No gel 1h 12 days. Chlownitro com 0 d g 6 mg lme l-chloro-l-nitro-Z-methyl-propane.- Do. p m eHZ-O naphpha 2-chl0ro-2-nitrobutane 1 74 hours. Solution sohmon A mixture of l-ohloro-l-nitro-ethane, l-chloro- 111 hours.

l-mtropropane and Z-O IO- P D Blank 33 hours. 138 hours.

l-chloro-Z-methyl-2-11itrobutane No gel in 12 No gel in 12 Example III days days' The rubber stock employed in Example II was Example VII dissolved in naphtha in a concentration equ1va- The rubber t k 1 d lent to 5% by weight of rubber, various chloro- 5 0c emp q m Example II was dissolved in benzol and in naphtha, 1n concennltro compounds were lncorporated in separate t rations equivalent to 5% by weight of rubber. portions of the resulting solut1on, in a concen- 1 1 -bromo-1-n1tropropane was incorporated in tration of 5% by weight and the solut1ons were o por ions of the solut1ons in a concentration of observed over a period of 12 days at 122 F. The 5 b h following results were secured y We1g t, and the resulting solut1ons were observed over a period of 12 days at 122 F. The

following results were secured: Chloronitro compound Gelling time Gellin t G 1- g i t 12 d Bromonitro compound ben zoi irig fi tfif -0 OIO- -Ill roe 8.1160 0 go 111 8. S. l-l-dichloro-l-nitroethane D0. y sohmon solutlim l-ohloro-l-nitropropane. Do. 1-1-dichloro-l-nitrcpropane D0- Blallk 11 5- 46 hours.

l-bromo-l-mtropropane No gel in 12 No gel in 12 days. days. Example IV The rubber stock employed in Example II was I do not wish to limit myself to the halogenated 4 dissolved in benzol and i naphtha, in concennitroparaffins indicated in the above examples 2,297,871 since in the practice of my invention I have found that the halogenated nitroparafiins generally may be used. Mixtures of these halogenated nitroparaflins, such as are Obtained by the chlorination of the products obtained by the direct nitration of the paraffin hydrocarbons may be used, as well as solutions of the halogenated nitroparafiins in other organic solvents, such as for example, alcohols, ketones, esters, and the like.

The choice of the particular halogenated nitroparaffin to be used will depend largely on the properties desired in the cement. The amount of halogenated nitroparafiin to be employed, in each individual case will depend on a number of factors such as for example, the particular halogenated nitroparafiin utilized, the character of the rubber cement treated, the amount of rubber contained therein, etc., as well as the effect of the particular halogenated nitroparaffin upon rubber. For example, l-chloro-lnitropropane is a good solvent for masticated rubber Whereas, 1,1-dichloro-l-nitropropane dissolves the same rubber only fairly well, and the 2-chloro-2-nitr0propane only slightly swells the rubber. Where, therefore, the particular halogenated nitroparafiin being used is a good or even fairly good solvent for rubber no particular difficulties are experienced in incorporating relatively large proportions of the halogenated nitroparaflin in the cement, but in cases where the halogenated nitroparafiin selected is not a rubber solvent, it can be incorporated into cements only in amounts up to those somewhat less than are required to precipitate the rubber from solution. Cements that have a tendency to form vulcanized gels in a relatively short time at atmospheric temperatures will, in general, require more halogenated nitroparafhn to stabilize the solution than in the case of cements of a more stable character. The exact amount of halogenated nitroparafiin to be used in a particular rubber cement may be readily ascertained by determining the tolerance of a cement for a particular halogenated nitroparafiin which it is desired to use and by determining the gelling time, at elevated temperatures, of cements containing slightly less than the amount of halogenated nitroparaflin required to efiect coagulation of the rubber in the cement. Where the halogenated nitroparafiin is a rubber solvent it may be incorporated in the cement in amounts up to 100% by volume of the cement but such amounts are generally unnecessary and usually amounts ranging from 0.5%, or even less, up to or 20% will give adequate protection.

I do not wish to be limited in any manner as to the specific ingredients that are incorporated into the rubber cement, for example, rubber may be used which has or has not been pre-masticated. The solvent may be any that is satisfactory for the purpose, such as gasoline, benzol, varnish and paint; makers naphtha, carbon tetrachloride, ethylene dichloride, etc. Fillers such as carbon black, clay, pigments, etc., and softeners such as mineral oil, and the like, may be added to the cements. vulcanizing agents and accelerators may be selected which are known to be useful for their purpose. I do not wish to be limited as to themanner in which the halogenated nitroparafiin is to be incorporated into the cement. This may be done at any time during the process of manufacture but previous to the time when a gel begins to form.

Having described my invention, what I claim is:

1. The improvement in the manufacture of heat vulcanizing rubber cements which comprises reducing the tendency of said cements to forms vulcanized gels on standing at ordinary temperatures by incorporating therein a halogenated nitroparafiin selected from the group consisting of chloroand bromonitroparaffins having not more than eight carbon atoms, in an amount sufiicient to retard the vulcanized gelling of the cement on standing.

2. The improvement in the manufacture of heat vulcanizing rubber cements which comprises reducing the tendency of said cements to form vulcanized gels on standing at ordinary temperatures by incorporating therein a halogenated nitroparafiin selected from the group consisting of chloroand bromonitroparafiins having not more than eight carbon atoms, in an amount sufiicient to retard vulcanized gelling of the cement on standing and less than is required to precipitate rubber from the cement.

3. The improvement in the manufacture of heat vulcanizing rubber cements which comprises reducing the tendency of said cements to form vulcanized gels on standing at ordinary temperatures by incorporating therein a chloronitroparaflin having not more than eight carbon atoms, in an amount sufficient to retard vulcanized gelling of the cement on standing and less than is required to precipitate rubber from the cement.

4. The improvement in the manufacture of heat vulcanizing rubber cements which comprises reducing the tendency of said cements to form vulcanized gels on standing at ordinary temperatures by incorporating therein a bromonitroparafiin having not more than eight carbon atoms, in an amount sufficient to retard vulcanized gelling of the cement on standing and less than is required to precipitate rubber from the cement.

5. The improvement in the manufacture of heat vulcanizing rubber cements which comprises reducing the tendency of said cements to form vulcanized gels on standing at ordinary temperatures by incorporating therein a monochloronitroparafiin having not more than eight carbon atoms, in an amount sufficient to retard vulcanized gelling of the cement on standing and less than is required to precipitate rubber from the cement.

6. The improvement in the manufacture of heat vulcanizing rubber cements which comprises reducing the tendency of said cements to form vulcanized gels on standing at ordinary temperatures by incorporating therein a monobromonitroparaffin having not more than eight carbon atoms, in an amount sufficient to retard vulcanized gelling of the cement on standing and less than is required to precipitate rubber from the cement.

7. The improvement in the manufacture of heat vulcanizing rubber cements which comprises reducing the tendency of said cements to form vulcanized gels on standing at ordinary temperatures by incorporating therein a dichloronitroparafiin having not more than eight carbon atoms, in an amount sufficient to retard vulcanized gelling of the cement on standing and less than is required to precipitate rubber from the cement.

8. A heat vulcanizing rubber cement containing a halogenated nitroparafiin selected from the group consisting of chloroand bromonitroparaffins having not more than eight carbon atoms, in an amount sufi'icient to retard the vulcanized gelling of the cement on standing.

9. A heat vulcanizing rubber cement containing a halogenated nitroparaffin selected from the group consisting of chloroand bromonitroparaffins having not more than eight carbon atoms, in an amount sufficient to retard vulcanized gelling of the rubber cement on standing and less than is required to precipitate rubber from the cement.

ARTHUR W. CAMPBELL. 

